如何给导航栏上的backButtonItem设置action？

Question

如何给导航栏上的backButtonItem设置action？我有一个导航栏，当我按下后退按钮时，我需要向用户提醒一些消息，并且只有在用户做出反应后才返回到上一个视图。我该怎么做呢？谢谢！

- (void)viewDidLoad 
{
    [super viewDidLoad];

    //no one field don't changed yet
    isDirty = FALSE;

    //edited user
    //set default values
    newData = [data copy];

    //setting navigation controller rigth button
    UIBarButtonItem *rightButton = [[UIBarButtonItem alloc] initWithTitle:@"Save"
                                                                style:UIBarButtonSystemItemDone 
                                                                   target: self 
                                                                   action: @selector(saveBtnUserClick)];
    self.navigationItem.rightBarButtonItem = rightButton; 
    [rightButton release];


    UIBarButtonItem *leftButton = [[UIBarButtonItem alloc] initWithTitle:@"Back"
                                                                   style:UIBarButtonSystemItemDone 
                                                                  target: self 
                                                                  action: @selector(backBtnUserClick)];

    self.navigationItem.backBarButtonItem = leftButton;
    [leftButton release];
}

//以及我的反应方法

-(IBAction) backBtnUserClick
{
    NSLog(@"\n Back pressed");

    //back to previous view
    [self.navigationController popViewControllerAnimated: TRUE];
}

Answer 1

这听起来像是 UIAlertView 的工作。不要在 IBAction 方法中调用 popViewControllerAnimated:，而是分配/初始化一个 UIAlertView 并呈现它。然后，当用户点击 UIAlertView 上的按钮时，关闭 UIAlertView 并调用 popViewControllerAnimated:。

- (IBAction)backBtnUserClicked:(id)object {
    UIAlertView *av = [[[UIAlertView alloc] initWithMessage:@"Wait!"
          delegate:self
               cancelButtonTitle:@"Ok"
               otherButtonTitles:nil] autorelease];
   [av show];
}

在您的 UIAlertViewDelegate 方法中调用 popViewControllerAnimated:。

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
    [[self navigationController] popViewControllerAnimated:YES];
}

要设置后退按钮的操作：

[[[self navigationController] leftBarButtonItem] setTarget:self];
[[[self navigationController] leftBarButtonItem] setAction:@selector(backBtnUserClicked:)];

Answer 2

使用 iOS 16 或更高版本时，您可以通过设置导航栏的 backAction 来插入自定义逻辑。例子：

navigationItem.backAction = UIAction(handler: { [weak self] action in
    
    // Your custom action here
    self?.myAlertAction()

    // Navigate one view controller back
    self?.navigationController?.popViewController(animated: true)
})

Answer 3

添加< UINavigationControllerDelegate >在头文件中并在 .m 中使用它

- (BOOL)navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem     *)item
{
  //insert your back button handling logic here
  // let the pop happen
  return YES;
}